Arc-extinguishing means for power switches having stationary and movable contact pieces



Nov. 24, 1964 a. BUECHNER ARC-EXTINGUISHING MEANS FOR POWER SWITCHESHAVING STATIONARY AND MOVABLE CONTACT PIECES 5 Sheets-Sheet 1 FiledMarch 5, 1961 INVf/QTOR GERHARD BUECHNER Nov. 24, 1964 G. BUECH'NERARC-EXTINGUISHING MEANS FOR POWER SWITCHES HAVI STATIONARY AND MOVABLECONTACT PIECES 5 Sheets-Sheet 2 Filed March 3, 1961 m y W NM w///\\\M//\\\\\\\\\\\\\\\\\\\ mm A M /l/ll/l/l l z W Aw 8 H W W xm .1 9 8I r///////////// Nov. 24, 1964 5. BUECHNER 3,158,723

ARC-EXTINGUISHING MEANS FOR POWER swrrcnas HAVING STATIONARY AND MOVABLECONTACT PIECES Filed March 3, 1961 5 Sheets-Sheet 3 Fig.3 I/VVENTOR:

GKRHARD BUEOINER ATTORIYIF) 3,158,723 ES HAVING 1964 G. BUECHNERARC-EXTINGUISHING MEANS POWER SWITCH STATIONARY AND MOV E commcw PIE.Filed March 3, 1961 I //v VEN TOR- GERHA RD 5 UECHNER BY Nov. 24, 1964G. BUECHNER 3,153,723

ARC-EXTINGUISHING MEAN OR P R S CHE-S HAVING STATIONAR Y AND M BLE TACIECES Filed March 3, 1961 5 Sheets-Sheet 5 INVEN TOR: GHPHARD BUECHNER-5y W i I ATTORNEY United States Patent rev any AND This inventionrelates to electric power switches having stationary and movable contactpieces, and ass particular reference to an improved arc quenching means.

it is known to improve certain characteristics and properties of aswitch, such as its freedom from arcingback, with the aid of forcedfluid flow. For example, a pump piston moving with the contact pin canproduce a fluid flow which washes the tip of said pin. Another knownpossibility is the injection of the arc quenching fluid into theextinction chamber, by a displacement brought about by the moving pinitself. Pump pistons provided with a special drive mechanism are alsoused for this purpose. A further method consists in producing anauxiliary are for building up the pressure, wnereby a fluid flow aimedthe principal arc may be a nod. The last-mentioned method has thedisadvantage that it depends on the intensity of the arc-current.However, the requirements or modern switch-gear, such as freedom fromarcing-back when switching capacitive currents on and oil, call for acurrent more or less independent of the size of the switclroli current.The means opera c with pistons are of relatively si e construction arugged in operation. They, howeve have disadvanage that only one of thecontact pieces is washed by the iluid current. it is, however, of greatadvantage for are extinction that both are bases be washed by the fluid.This has been unequivocally corroborated by the l and experimentalinvestigations. The process or circurnilow may e realized in cases wherethe is held ready under pressure at all times, such as in an blastcircuit-breakers. Washing of both contact pieces then is only a questionof the proper arrangement of the quenching elements. To sucllend,however, additional storage means is required which always has to malccavailable the requisite quantity of pressurized fluid, even when notactuating the switch. in such case, however, the guarantee that thequencl'iing capacity of the switch is maintained at all times, issubstantially smaller than in the case of follow-up pistons and the lil;

The deficiencies of the known mean of this type may be avoided byproviding, in accordance with the teachings of the present invention,two concentric insulating tubes extending in direction of the switch-rodpath. The

gap between these two tubes leads to an annular nozzle in the vicinityof a pair of stati nary contact pieces, and said gap has a furthercommunication to the interior of the extinguishing means the vicinity ofa pair of movable contact pieces which cause at least two fluidcurrents.

The advantage of the invention resides in the fact that the two pairs ofstationary and movable contact pieces are washed by fluid without needfor any additional storage means, and that tile s ace between thestationary ice and the movable contact pieces is subjected to a fluidcurrent which is adjusted to the quenching conditions.

Forms of the invention are shown, by way of example, in the drawing, inwhich:

FIG. 1 shows a first form in vertical section; FIG. 2 illustratesschematically and on a much larger scale the position of the movablecontact or burning pin shortly after separation of the metallic currentpath, i.e. shortly after creation of an arc; FIG. 3 sin r to FIG. 2showthe lower position of the contact pin and contact head; 4- depicts asecond form of the invention in a manner similar to 1; MG. 5 shows athird form with a different nozzle contact piece; am. EEG. 6 illustratesa fourth form with a pair of movable contact p eces affording animproved guiding of fluid along the burning contact Like carts aredesignated by the same numerals throughout the drawings. All thearrangements shown are sections of a complete switchgear unit. T .16invcntion may be used with gaseous and liquid quenching agents, and forlow and high-tension switches.

in FIG. 1 a iiange provided with a ter iinal or point of current supplyis screwed to the upper lio'. To said flange is secured a metallicsleeve which holds the exterior insulating tube in the latter isdisposed an intermediate tube also made of insulating material. The tube5, together with an interior insulating tube 5, forms a plurality ofchannels and betwce these tubes. This communication terminates at itsupper end in an inwar y directed annular nozzle-like gap 9/. At itslower end, openings 7 lead to the interior of the tube 4. Tube t at itslower end is closed by the metallic sleeve 19 and a flange screwedthereto which comprises a terminal or point of current supply ll.

serve as stc onary current conductors or Contact pieces as well as forguiding gas now. On body E3 is seated the laminated conact piece whichthe on-state of a metallic connection with the on the movable switch rod126. The movable contact piece includes also a central part i? which ispositioned in body 15 in the switch-on s. without, however, carrying anysubstantial current on. account of the great contact resistance. At therear end of the movable contact piece is a piston defining formation 21.s e a cylinder within which the piston 21 moves. This der is filled withquenchi g fluid. From rod 1- electric current is cond'cc contact pieceis and the inter, iezliate piece to the current terminal it. in ahousing is disposed the mechanism for moving rod 16, which may cosuitable means. Upper housing 1 is suitably for a butter chamber or maycontain npers tors of known type.

in FIG. 2, contact head 15 with its pistonlilre lug has been moved sli'htly out of the switch-on position. An arc has been formed between headIf and a lamination of contact piece is. Further, the descending nistonZli has displaced quenching fluid. At the beginning of the .iovernent ofthe piston in switch-opening direction there is the possibility thatquenching fluid will flow over the piston laterally and escape along 1'7through the nozzle opening in the position shown, the piston has 3 justclosed the annular flow-in space 23. On the other hand, gap 9 has justbeen uncovered by the upper edge of head 15. Piston 21 thus moves thefluid behind it through the openings '7 (FIG. 1) into the channels 8,whence it flows in a directed beam from gap 9. The short are 24 therebyis forced to form a loop which finally contacts body 13 so that a neware base is established there, while the arc base on one of thelaminations 1.4 is extinguished. Also, the arc base of the movablecontact piece changes, under the action of this fluid current, from theupper rim of head 15 to the burning tip 17. In this manner, the twocontact functions, namely constant current contact and are contact, maybe carried out separately and by means of different materials. Duringthe further descent of head 15, piston 21 continues to move the fluidthrough the channels and gap 9, and the fluid escapes through body 13.The re base is thus shifted into the interior of nozzle 13, the extentof such travel depending on the flow intensity. In order to avoid, inthe case of very pronounced fluid currents such as shortcircuitdisconnections resulting from a heavy current produced by the arcitself, any unnecessarily great extension of the arc in its travel, alimiting pin 112 (Fl 1) may be provided. The nozzle 13 has the particulrly important function of screening the hot spot at the are base (whichstill emits electrons long after the arc been cxtin guished), with theaid of the advanced cold nozzle rim.

After having moved a certain distance, contact head 15 reaches theposition shown in FIG. 3. It will be noted that the interior of thecylinder is provided with annular recesses exemplified by the regiondesignated 23. These recesses are more closely spaced in the regionoccupied by the piston 21 during the initial portion of its stroke thanin the region occupied by the piston during the later portion of itstravel. As a result, the contact between the piston and the cylinder isgreater during the initial portion of its stroke than later, wherebyless fluid travels past the piston during the earlier part of the pistontravel.

In FIG. 3, piston 21 has just left the portion of the interiorinsulating tube 6 which has the more closely spaced recesses, mid nowlaterally uncovers a much longer annular space. The fluid from the spacebelow the piston thus can more freely flow around the piston in theaxial direction of the cylinder, and thus flow directly along pin 17.The cross-sections of the openings in t. e piston and those of thechannels 8 and of the gap 9 are so graded that the fluid current whichpreviously flowed through the channels 8 now follows both paths and isdivided in a predetermined ratio. The result is that the interior spaceabout the are which previously had been washed only to a limited extent,now is intensively washed in the vicinity of the quenching position, andthe arc column is thus cooled. The fluid flow about pin 17 which stillcontinues after the arc has been extinguished, electrically screens theemitting hot spot left there from the switching path. For similarreasons, provision also has been made that the flow from gap 9 ceasesonly when the switching path has again been sufficiently consolidatedelectrically. Such flow of fresh fluid well insulates or screens theupper fixed contact pieces.

In the example shown in FIG. 4, tubular stationary contacts 25, 26 areprovided in place of the laminated contact pieces 14, 18 of FIGS. 1 t03, and the movable contact head as well as the switch rod is formed as atubular contact piece 27. Pin 17 corresponds to the former design, Whilein the former example, however, the piston producing the quenching fluidflow was an integral part of the reciprocable switch rod, 21 fixedpiston 2% is used here. It is, however, also possible to use a pistonwhich is driven in the opposite direction by the contact tube, forexample by means of any suitable reversing gear. The other structuralcomponents correspond to those of FIG. 1, and the mode of operation ofthe example shown in FIG. 4 is as follows:

As soon as contact tube 27 through any suitable driving mechanism (notsh wn) is mo ed downwardly from the switch-on position, it displacesfluid from its interior due to the action of fixed piston 23, and thefluid flows along pin 17. The fluid present in the space between tube 6and tube 27 is forced by a collar 29 on the outside of tube 27, whichcollar slides snugly in tube 6, through the openings 7, channels 8 andgap past nozzle contact 13 and through the opening in latter into thebuffer chamber Further, when contact tube 27 moves into the drivehousing as, the fluid present in the latter is displaced and flowsthrough compensating bores 31, the openings 7, channels 8 and gap 9 tothe fixed contact pieces 13 and 25.

In the example shown in HG. 5, I: again is the metallic flange whichholds tne exterior insulating tube 4-. The intermediate insulating tube5, the interior insulating tube 6 and gap 9 formed by the two tubescorrespond to the parts of FIG. 1. The nozzle body 13 is practicallyunchanged in its outside dimensions. Additionally, however, bores 32have been provided in upper portion, while the lower portion is formedas a sliding contact piece. The latter may be of any suitable nozzlelikeconstruction. In the drawing, contact piece 33 is a slotted piece oftube with an annular ring in the switch-on position, the exteriortubular contact piece 25 as well as the interior nozzle contact-piece 33are in metallic contact with the movable contact counterpieces 1'7 and15 or 27. It is of advantage to so form the contact pieces that theinner pair of contact pieces 33, 17 is separated last during theswitch-off procedure. The holes erve to enhance the fluid flow. Sincethe cross-sccticn of the openings in the nozzle contact piece 33possibly may not sufflce for the quick discharge of fluid, additionalventing means may be provided by increasing the number of bores 32.

In the form of invention shown in FIG. 6, a cap 35 having a central boreas is movable in contact tube 27. The lower edge of the cap is providedwith a plurality of openings 37. The position shown corresponds to theposition of contact tube 27 at the end of the switch-off movement. Abottom lug 30 of contact pin 1'7 has entered a damping bore of fixedpiston 28. Bores 4d disposed laterally of pin 17 serve for lettingquenching fluid flow from the space above piston During the switch-offmovement, the displaced fluid flows through the bores 4% along pin 27and through bore as of cap 3 into the quenching space. The openings 37are closed by a bulge ti on contact tube 2". These openings serve forproviding, during the switching-on movement, a possibility or reverseflow for the fluid present in front of cap 35, as then bore 36 indepressed cap 35 is fully occupied and closed by pin 17. The collar 29provided on contact tube again produces, during the switch-off movement,the second fluid current through the openings 7, channels 3 and gap 9 tothe fixed contact pieces. The compensating bores 31 in the lowermetallic body Til allow the fluid to balance its pressure in thechannels 8 and the drive housing What I claim as new and desire tosecure by Letters Patent, is:

An electric switch including stationary and movable contact pieces andarc-quenching means, each of said contact pieces comprising a centralarc-carrying contact and an annular current-carrying contact surroundingand spaced from said central contact; said current-carrying contactsbeing adapted to engage to close the switch and to disengage to open theswitch, disengagement of said currentcarrying contacts engendering anare between them; said arc-quenching means includin an annular nozzlesurrounding said current-carrying contacts, means for directing a fluidblast through said nozzle toward the interior of said annular contactsin order to shift the are from said current-carrying contacts to saidarccarryiug contacts, and means for directing a fluid blast along the ofsaid current-carrying contacts after said nozzle-directed blast has beeneffective long enough to shift the arc, said fluid-directing meansincluding a piston movable with said movable contact piece and acylinder within which said piston moves, the interior surface of thecylinder having annular recesses so spaced that during the initialportion of the piston stroke in the direction of switch opening thecontact between the piston and cylinder is greater than during the laterportion of the piston stroke, said cylinder being filled with quenchingfluid and being provided with a communication between the region behindthe piston and said annular nozzle, whereby the blast created duringsaid initial portion of piston travel is directed mainly through saidcommunication while the blast created during the later portion of pistontravel is mainly past said piston in the axial direction of thecylinder.

References Qited in the file of this patent UNITED STATES PATENTSFOREIGN PATENTS Sweden Nov. 10, 1936 Switzerland July 1, 1950 AustriaFeb. 10, 1955 Great Britain Dec. 18, 1941

